Fixed regenerate mode, added to schema.

makko.schema.json

···
         "symlinks_enabled": {
           "type": "boolean"
         },
+        "cleanup_mode": {
+          "type": "string",
+          "enum": ["regenerate", "none"]
+        },
         "source": {
           "type": "string"
         },

src/Makko.zig

···
 
     if (!helper.exists(root_dir, paths.output))
         try root_dir.makeDir(paths.output);
-    const output_dir = try root_dir.openDir(paths.output, .{});
+    const output_dir = try root_dir.openDir(paths.output, .{ .iterate = true });
 
     if (paths.symlinks_enabled and !helper.supports_symlinks) {
         log.warn(